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pH problems

pH problems. pH equations. pOH = -log [OH - ] pH = -log [H + ] [H + ][ OH - ] = 1x10 -14 pH + pOH = 14 pOH is the reverse of pH Above 7 is acidic, below 7 is basic. Sig Figs and pH.

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pH problems

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  1. pH problems

  2. pH equations • pOH = -log [OH-] • pH = -log [H+] • [H+][OH-]= 1x10-14 • pH + pOH = 14 • pOH is the reverse of pH • Above 7 is acidic, below 7 is basic

  3. Sig Figs and pH • The number of decimal places in the log value, pH value, is equal to the number of significant figuresin the number that we took the logarithm of, concentration. • So [H3O+] = 2.45 x10-4 M 3 sig figs • pH = -log 2.45 x10-4 M = 3.611 • 3 decimal places

  4. pH problems • What is the pH of a 2.4 x 10-4 M H3O+? • pH = - log 2.4 x 10-4 • pH = 3.62 • What is the OH- concentration? • [H3O+] [OH-] = 1 x 10-14 • 2.4 x10-4 [OH-] = 1 x 10-14 • [OH-] = 4.2 x10-11 M • What is the pOH? • pOH = - log 4.16666x10-11 • pOH = 10.38

  5. Backwards problem • What is the pOH, [H3O+] and [OH-] of a solution with a pH of 8.72? • [H3O+] = 10^(-pH) • [H3O+] = 10-8.72 • [H3O+] = 1.9 x 10-9 M • 1.905…x10-9[OH-] = 1 x 10-14 • [OH-] = 5.2 x 10-6 M • pOH + pH = 14 • pOH = 5.28

  6. Problem • What is the pH, pOH and [H3O+] of a soln. with a [OH-] conc. of 2.90 x10-4 M? • [H3O+] 2.9 x 10-4 = 1 x 10-14 • [H3O+] = 3.45 x 10-11 M • pH = -log 3.448275 x 10-11 • pH = 10.462 • 10.47 + pOH = 14 • pOH = 3.538

  7. Problem • What is the pH, [OH-] and [H3O+] of a solution with a pOH of 11.1? • 11.1 + pH = 14 • pH = 2.9 • [H3O+] = antilog (-2.9) • [H3O+] =1 x10-3 M • [OH-] = 8 x10-12 M

  8. Another • What is the pH, pOH, and [OH-] of a solution with a [H3O+] of 4.90x10-8 M? • pH = - log 4.90x10-8 • pH = 7.310 • [OH-] = 2.04 x10-7 M • pOH = 6.690

  9. More • What is the pH, pOH and [H3O+] of a solution with a [OH-] of 1.78x10-12 M? • pH = 2.250 • [H3O+] = 5.62 x10-3 M • pOH = 11.750

  10. Continuing • What is the [OH-] and [H3O+] of a solution with a pH of 9.43? • [H3O+] = antilog (-9.43) • [H3O+] =3.7 x10-10 M • [OH-] = 2.7 x10-5 M • pOH = 4.57

  11. Last one • What is the pH and [OH-] of a solution with a [H3O+] of 2.7x10-6 M? • pH = - log 2.7x10-6 • pH = 5.56 • [OH-] = 3.7 x10-9 M • pOH = 8.44

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